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DESIGN REQUIREMENT CLARIFICATION FOR BODY AREA NETWORK (BAN)

CHEAH EE LING

UNIVERSITI TUNKU ABDUL RAHMAN

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DESIGN REQUIREMENT CLARIFICATION FOR BODY AREA NETWORK (BAN)

CHEAH EE LING

A project report submitted in partial fulfillment of the requirements for the award of Bachelor of Engineering

(Hons) Biomedical Engineering

Faculty of Engineering and Science Universiti Tunku Abdul Rahman

April 2011

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DECLARATION

I sincerely declare that this project report is based on my original work except for citations and quotations which have been duly acknowledged. I also declare that it has not been previously and concurrently submitted for any other degree or award at UTAR or other institutions.

Signature :

Name : Cheah Ee Ling ID No. : 07UEB08710 Date : 15th April 2011

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APPROVAL FOR SUBMISSION

I certify that this project entitled “DESIGN REQUIREMENT CLARIFICATION FOR BODY AREA NETWORK (BAN)” was prepared by CHEAH EE LING has met the required standard for submission in partial fulfillment of the requirements for the award of Bachelor of Engineering (Hons) Biomedical Engineering at Universiti Tunku Abdul Rahman.

Approved by,

Signature :

Supervisor : Mr. Chuah Yea Dat Date :

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The copyright of this report belongs to the author under the terms of the copyright Act 1987 as qualified by Intellectual Property Policy of Universiti Tunku Abdul Rahman. Due acknowledgment shall always be made of the use of any material contained in, or derived from, this report.

© 2011, Cheah Ee Ling. All right reserved.

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Specially dedicated to

My beloved grandmother, father and mother

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ACKNOWLEDGEMENTS

I would like to thank everyone who had contributed to the successful completion of this project. I would like to express my gratitude to my research supervisor, Mr.

Chuah Yea Dat for his invaluable advice, guidance and enormous patience throughout the development of the research.

In addition, I would also like to express my utmost gratitude to Prof. Ryiochi Komiya who had helped and guided me a lot along the completion of this research project.

Also, I would like to thank all participating medical doctors and biomedical engineering personnel who have contributed in completing my survey questionnaire.

Their patience and cooperation in the information sharing session is highly appreciated. In such a case, I would like to highlight my acknowledgement especially to Dr. Andy Yong, Dr. Sumitra, Mr. Nitin Tadas Wamanrao, Encik Azman Hamid, Mr. Marvin Rich, Ms. Michelle, Encik Haris, Mr. Teoh Boon Chong, Mr. Alfred Eng Ho Shin and Mr. Christopher Montana.

Although travelling around the private hospitals (particularly in Kuala Lumpur and Penang) can be quite tiring, I admitted that I gained a lot of precious information through the survey conducted, which cannot be retrieved on the textbook solely. This definitely helps a lot in aiding my understanding and further interpretation regarding BAN system. Based on the ascertained design requirements, we shall thereafter have a clear concept in developing a BAN based, human friendly, connected health system.

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Last but not least, I wish to express my deepest thanks to my family for their unconditional love and support. Their sincere caring and support had helped me successfully completing my dissertation.

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TABLE OF CONTENTS

DECLARATION iii

APPROVAL FOR SUBMISSION iv

ACKNOWLEDGMENT vii

TABLE OF CONTENTS xiiix

LIST OF TABLES xxivii

LIST OF FIGURES iv

CHAPTER

1 INTRODUCTION 1

2 LITERATURE REVIEW

2.1 Body Area Networks 4

2.1.1 BAN sensor nodes design 4

2.1.2 BAN block diagram 7

2.1.3 BAN data exchange 8

2.1.4 BAN communication 9

2.1.5 BAN signal traffic 11

2.1.6 BAN power supply 11

2.1.7 BAN signal measurement principle 12

2.2 Prospective BAN contribution to patients and medical people 15 2.3 BAN International Applications 16 2.3.1 Cardiovascular disease detection applications 17

2.3.2 Cancer detection applications 18

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2.3.3 Asthma detection applications 18

2.3.4 Artificial retina applications 18

2.3.5 Sleep disorder detection applications 18

2.3.6 Intelligent control of medication applications 19

2.3.7 Predictive diagnostic applications 21

2.3.8 Biomedical feedback control systems applications 21 2.3.9 Battlefield applications 22

2.4 Challenges 23

2.4.1 Hardware Level Challenges 23

2.4.1.1 Unobtrusiveness 23

2.4.1.2 Sensitivity 23

2.4.1.3 Energy 23

2.4.1.4 Data acquisition efficiency 24

2.4.1.5 Reliability 24

2.4.2 Layer Independent Challenges 24

2.4.2.1 Security / Privacy 24

2.4.2.2 User-friendliness 25

2.4.2.3 Cost 25

3 METHODOLOGY 3.1 Introduction 25 3.2 Source of Data 26 3.2.1 Primary Data 26

3.2.2 Secondary Data 26

3.3 Selection of Research Strategy 27 3.3.1 Literature Review 27

3.3.2 Questionnaire Survey 27

3.4 Data Analysis 28

3.5 Flow chart of research progress 29

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4 DATA ANALYSIS

4.1 Respondent’s demographics 32

4.1.1 Respondent's working experience years 32

4.1.2 Respondent's occupation / positions 33

4.1.3 Nature of respondent's sectors 34

4.2 Findings from Questionnaire Surveys (Part 1 : In-patients) 36 4.2.1 Response of respondents towards BAN implementation within hospital 36

4.2.2 Best implementation site for BAN within hospital 40

4.2.3 Main problems about BAN System 43

4.2.4 Target diseases for BAN system 45

4.2.5 BAN requirement for cardiovascular patients 45

4.2.6 BAN requirement for hypertension patients 49

4.2.7 Types of post surgical patients suitable for BAN 50

4.2.8 Post surgical complications (importance index) 52

4.2.9 BAN requirement for after - surgery patients 53

4.2.10 Other findings 4.2.10.1 Preferable types of battery 55

4.2.11 BAN design 58

4.3 Findings from Questionnaire Surveys(Part 2 : Out-patients) 62

4.3.1 BAN Target for Home Monitoring Purposes 62

4.3.2 BAN requirement for Cardiovascular Patients 64

4.3.3 BAN requirement for Hypertension Patients 66

4.3.4 Response of respondents towards idea of wireless cardiac event monitor 67

4.3.5 Main concern about BAN system 68

4.3.6 Other findings 70

4.3.6.1 Suitability of BAN for Obstrusive Sleep Apnea patients 70

4.3.6.2 Preferable types of battery 71

4.3.7 BAN design 73

4.4 Findings from Questionnaire (Part 3 : health-consicous) 74 4.4.1 Application of BAN to health conscious people 75

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4.4.2 BAN target for health conscious people 76

4.4.3 BAN measu3ent for health conscious people 78

4.4.4 Preferable BAN design types 79

4.4.5 Main concern about BAN system 82

4.4.6 BAN design 84

5 CONCLUSION AND RECOMMENDATION

5.1 General conclusion from project 85

5.1.1 In-patients 87

5.1.2 Out-patients 88

5.1.3 Health conscious people 89

5.2 Recommendation 90

REFERENCES 90

APPENDICES 96

Questionnaire Survey

Feedback Report from Surveys

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LIST OF TABLES

TABLE TITLE PAGE

1 Summary of the 4 sensor node generation 6

2 Bandwidth required for real-timesignal transmission 10

3 In-body and on-body sensor network applications 16

4 List of hospitals & companies included in surveys 31 5 Comparison between wired telemetry system and

wireless BAN system 39

6 Comparison of BAN implemnetation architecture design between in-patients, out-patients and health

conscious people basis 84

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LIST OF FIGURES

FIGURE TITLE PAGE

1 Years of working experience among respondents 32

2 Respondent’s occupations 33

3 Types of respondent’s sectors 34

4 Response of respondents towards implentation of

BAN within hospital 36

5 The best implentation for BAN within hospital 40

6 Main concern about BAN system (from respondents) 43

7 Target diseases for BAN system 45

8 BAN requirement for cardiovascular patients 47

9 BAN requirement for hypertension patients 49

10 Types of post surgery patients for BAN 50

11 Post surgical complications 52

12 BAN requirement for post surgical patients 53

13 Preferable types of battery maintenance 56

14 BAN design (for in-patients) 60

15 BAN target for home monitoring purpose 62

16 BAN requirement for cardiovascular patients 64

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17 BAN measurement for hypertension patients 66 18 Response of respondents towards idea of wireless

cardiac event monitor 67

19 Main concern about BAN system (from respondents) 68

20 Preferable types of battery maintenance 71

21 BAN design (for out-patients) 74

22 Application of BAN to health conscious people 74 23 BAN target diseases for health conscious people 76

24 BAN measurement for health conscious people 78

25 Preferable BAN design for health conscious people 79

26 Main concern about BAN system (from respondents) 82

27 BAN design (for health conscious people) 82

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CHAPTER 1

INTRODUCTION

Body Area Network (BAN) is one promising application in the integration of sensing and consumer electronics technologies which would allow people to be constantly monitored (Schmidt, A., Laerhoven, K.V., 2001). It enables a ubiquitous remote medical device which can provide patients with assistance everywhere, anywhere and at any time.

In the near future, healthcare will face major challenges as medical costs are rapidly increasing worldwide due to widespread chronic diseases and aging population. In such a case, the ageing population is due to the combined effect of falling birth rates and increasing life expectancy. Recent statistics showed that the percentage of ageing people in Malaysia was increasing. In 2000, the number of elderly people was 1.45 million or 6.2% of the total population but in 2009, the number increased to 2.03 million or 7.1% of the total population. Twenty five years down the line, Malaysia is likely to reach an ageing nation status by 2035 with the number of people above the age of 60 reaching 15% of the population. In such a case, the United Nations categorizes any country with 10% of its population above the age of 60 as an ageing nation. (The Star, 2010) On the other hand, chronic diseases are persistent or recurring conditions that require care for more than a year and that limit the patient‟s activities. Although there is no definite cure for a chronic disease, it can be managed to reduce its effects on the patient at a minimal level.

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Also, there is a situation where hospital beds not being able to meet the number of patients to be admitted. Furthermore, chronic patients discharged from hospitals, elderly and the disabled are desperately in need of intensive monitoring at home. The cost of sensing nurses or medical doctors to attend patients at home is very high. Therefore, the rationale of my research is to solve the problems stated above to at least, a minimal level. In such a case, the traditional cable sensors however, often cause inconvenience to patients by restricting patient‟s mobility and disturbing them with the presence of cables. To overcome this problem, wireless medical sensors are developed and applied. (Guo, Kang, Cao & Zhang, 2008) Admist all the effects on biomonitoring, we see the potential of using low – power consumption, light weight and integrated physiological sensors for detection of sentinel events among in – patients and out – patients as well. In maintaining the general health of people, it can be useful to remotely monitor their health status in their daily lives as well too. (Togowa, 1998)

Well, the aim in this research is to clarify the design requirement which is needed for BAN. The scope of the research is to identify out the use cases of BAN and clarify specific vital sign sensors to be mounted on patients. In such a case, the functional specifications and design requirements may differ to suit different medical procedures. Thus, all these matters have to be discussed face – to face with medical doctors and biomedical engineering personnel from Malaysia‟s private and government hospitals.

In order to do so, the objective in this research is:

 To understand the application of connected health system in patient health monitoring.

 To understand the BAN architecture and its functionality

 To develop and apply interpersonal skills when conducting interview with medical doctors and specialists during interview session. In such a case, presentable soft skills are needed as to let them understand the concept of such system and to collect their medical point of view.

 To develop data analysis technique in analyzing data.

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This BAN research is only mainly concentrating in hospitals around Kuala Lumpur and Penang. The participating respondent in this research were 30 people.

They are consisted of 10 medical doctors and 20 biomedical engineering personnel.

Based on the ascertained design requirement (which can be obtained from their professional knowledge), we shall thereafter develop a BAN – based, human friendly, connected health system.

The first chapter of this progress report is about the introduction of the BAN.

The second chapter is about the literature reviews which have been done based on the journals and articles related with BAN. In such a case, one way of attaining information is through the current mass media and publications. These reviews are important in such a way that they provide the latest development especially from the biomedical field. Lastly, the third chapter is about the methodology to define the methods to conduct this research. The methods included here such as literature review, questionnaire survey and also data analysis.

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CHAPTER 2

LITERATURE REVIEW

2.1 Body Area Network

The current common goal in medical information technology today is the design and implementation of telemedicine solutions, which provide to patients services that enhance their quality of life. Recent technologies advances in sensors, low – power integrated circuits, and wireless communications have enabled the design of low – cost, miniature and intelligent physiological sensor modules. These modules are capable of measuring, processing, communicating one or more physiological parameters, and can be integrated into a wireless body area network. (Rotariu, Costin, Arotaritei & Constantinescu, 2008)

In such a case, the healthcare BAN consists of sensors, actuators, communication and processing facilities. Patient data is collected using a Body Area Network (BAN). A healthcare practitioner can view and analyze the patient data from a remote location. In this setting, the BAN acts as a provider of patient data and the healthcare practitioner acts as a user of that data.

2.1.1 BAN Sensor Nodes Design

Depending on types of patient data must be collected, different medical sensors are integrated into the BAN. For example, an oximetry sensor is attached to the patient‟s finger to measure their pulse rate and oxygen saturation. In the case of an ECG

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measurement, electrodes are attached on the patients‟ arms and chest. (Dokovsky, Halteran, Widya, 2003)

In bio – monitoring, the sensor nodes should be placed in close proximity of the subject‟s body. This constitutes a body – area network. The evolution of sensor node leverages all technology options available, from the every – shrinking standard microelectronic technology, to the emerging microfabrication processes (Benini, Farella, Guiducci, 2006). The evolutionary sequences of 4 sensor nodes generation are generally characterized by a decreasing level of obtrusiveness.

(i) Obtrusive

These devices are constantly perceived by the target subject due to their large size and weight. Many current commercial devices are obtrusive. For examples, holter ECG and body tracking systems based on wearable cameras and marker.

Disadvantage of such device is such a way they are too bulky to be applied on the daily monitoring purposes. Also, they may constrain normal behavior on patients.

(ii) Parasitic

These nodes are still perceived by the subject as physical objects, but their size, weight and structure are comparably less than obtrusive node in first generation. In such a case, the physical volume of these nodes should not exceed a few cubic centimeters, and their weight should be in the order of the tens of grams. For examples, parasitic devices are bio – metric watches and body – tracking inertial sensors. Advantage of such device is such a way that it does not pose serious limitation to normal behavior if compared to obtrusive sensor node devices.

(iii) Symbiotic

These nodes are called symbiotic since they have a mutual advantageous relationship with the target organism. In such a case, the nodes are more aggressively scaled and should be in cubic millimeters. Also, it should be bio – compatible to enable in – body bio – monitoring applications. Advantage of such devices is such a way that they do not pose limitation to normal behavior since they are implanted within the target organism. They are not being able to be observed. However, disadvantage is such that the biocompatibility of this sensor node have to be considered since it is in-

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body bio – monitoring applications. Once implanted, the device should not be rejected by the immune system by patients due to in – biocompatibility. The rejection here can be fatal, for sometimes.

(iv) Bio – hybrid

As an end point of out evolution trend, the physical scale of these devices approaches a few cubic microns (or less), and the interface between the sensor target and the sensor itself disappears. These devices operate autonomously, powered by chemical reactions inspired to biological systems. The construction process and the architecture of these devices will also resemble natural process in biology: bottom – up self – assembly, self – replication and self – repair. Advantage of such devices is such a way that they do not pose limitation to normal behavior since they are implanted within the target organism. They are not being able to be observed.

However, disadvantage is such that the biocompatibility of this sensor node should be considered since it is in-body bio – monitoring applications. Once implanted, the device should not be rejected by the immune system by patients due to in – biocompatibility. The rejection here can be fatal, for sometimes. (Benini, Farella, Guiducci, 2006)

The trend and the fundamental characteristics of the 4 generations of sensor nodes are summarized in Table 1.

Table 1: Summary of Sensor Node Generations (Benini, Farella & Guiducci, 2006)

Node Maturity Power (W) Size (m3)

Obtrusive Commercial 1 – 10-1 10-3

Parasitic Prototype / commercial 10-2 to 10-3 10-6 Symbiotic Research / prototype 10-5 to 10-6 10-9

Bio-hybrid Concept / research < 10-7 10-15

In this survey, the attention is paid on one specific sensor node application, which is parasitic sensor node. There are several reasons for the choice. Firstly, this sensor node is less obtrusive and does not pose serious limitation to normal behavior.

Secondly, its design does not take consideration of biocompatibility. Also, the technical challenges posed are not causing major problem with the state of the art.

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In general, a sensor network node hardware consists of several subsystems: a microprocessor, data storage, sensors, actuators, a data transceiver and an energy source. A sensor node is a multi – functional unit performing many different tasks, from managing acquisition to handling communication protocol schedule and preparing data packets for transmission, after filtering, synchronizing and signal processing on data gathered from sensors. Thus, each sensor node requires processing and storage capabilities. The choice of the processing unit not only decides the intrinsic “intelligence” of the node but also influences its size and power consumption.

Figure 1: Sensor Node Functional Components (Benini, Farella, Guiducci, 2006) 2.1.2 BAN basic block diagram

Sensor nodes are designed to be small and power efficient so that their battery can last for a long time. They are designed to collect raw signals from a human body. A sensor node undertakes 3 tasks: detecting signal, digitizing / coding / controlling for a multi access communication and finally wireless transmission via a radio transceiver technology. They collect the signals from a human body which are usually weak and couple with noise. For a reliable information transfer, it is necessary that the interface electronics in the sensor nodes detect the physiological signals in the presence of noise. The signal – to noise (SNR) of the detected signal should be increased for a better processing.

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Filtering process is to first remove the unwanted signals and noise. At such low frequency and low amplitude, amplification process is utilized to increase the signal strength. Then, an Analog to Digital (ADC) stage is employed to convert the analog body signals into digital for a digital signal processing. The digitized signal is processed and stored in a microcontroller. The microcontroller will then pack and transmit over the air via a wireless transceiver (Mehmet, 2010). Figure 3 shows a basic idea on hardware implementation of sensor nodes and the block diagram.

(Mehmet, 2010)

Antenna

ECG/EEG 10-bit

Amplifiers / ADC

Temp. Filter / Micro

Multiplexer Controller Radio Pulse Rate Transceiver

Figure 2: An Example of Implementation Block Diagram (Mehmet, 2010) 2.1.3 BAN data exchange

The data exchange may be done in one of two methods, which is real time or non – real time basis. In the case of real time basis communication, both users are simultaneously logged into the server. The data should be sent when the sensors are measuring vital signs. Though out such communication, both users are able to interact with each other in real time, establishing also video conference session, when is needed. On the other hand, in the case of non – real time basis communication, the users exchange messages and information in asynchronous mode.

(Sachpazidis, Kontaxakis & Sakas, 2009) The data is stored and can be sent after vital sign measurement has been completed. For example, the data can be attached as a file to e-email.

In this research, the BAN data can be sent to hospital / Medical officer‟s office in either real time or non real – time basis. For the application of BAN within

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the hospital (particularly for in – patients and medical tourists), the data is transmitted in real – time bases when the sensors are measuring vital signs. The advantage is such that medical personnel can be alerted when any sentinel events happens in real – time.

On the other hand, for home monitoring purpose on out – patients and health conscious people as well, non real – time basis data transmission is more applicable with the state of the art. Advantage is such that users can be monitored constantly if compared to the existing Holter system (which can only be used on monitoring purpose for 24 up to 48 hours). Rather than precise measurement, such BAN is useful for long – term monitoring on patients at home. The data is stored and analyzed by medical personnel or caregivers after a period of monitoring.

2.1.4 BAN communication

Communication between entities within a BAN is called intra – BAN communication.

Our current prototypes use Bluetooth for intra – BAN communication. To use the BAN for remote monitoring, external communication is required which is called extra – BAN communication. Figure 2.1 below shows the architecture of BAN.

Extra BAN communication Mobile Base Unit Sensors

BAN Actuators boundary

Figure 2: BAN Architecture (Dokovsky, Halteran & Widya, 2003)

The range and complexity of telecommunication technology vary with the specific medical application. Transmission of medical images would require more bandwidth. However, teleconsultations of ultrasound images require only a few

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megabytes of data. On the other side, transmission of vital signs might also need adequate bandwidth. The bandwidth needed for vital signs is depicted in Table 2.

Table 2: Bandwidth Required for Real – Time Transmission (Benini et al, 2006)

In this research, the signal transmission is mainly concentrate on ECG, pulse oximetry, heart rate and blood pressure. Integration of vital sign measurements are depending on the specific uses cases of BAN, and yet such integration have to researched and discussed with medical officers and specialists from Malaysia‟s private hospitals. Signal transmission of ultrasound images and video conference are not included in this research.

2.1.5 BAN signals traffic

In BAN, traffic between the biosensor and the controller can be classified into 2 major types: periodic traffic and aperiodic traffic. Periodic traffic is physiological signals measured at every fixed period (such as every 2 seconds). On the other hand, aperiodic traffic has no constraint of periodicity. Aperiodic traffic can be divided into alarming packets and control commands. In such a case, alarming packets are usually time – critical, because an emergency must be reported before a worse case situation occurs. (Guo, Kang, Cao, Zhang, 2008) But in practical case of this research, the alarm have to be made sure that it must not be frequent false alarm caused by human error. Else, the alarm might be ignored by caregivers when it comes to critical one.

Signals Bandwidth

ECG 1 lead 3,6KBit/second

ECG 12 leads 43,2 KBit/second

Pulse oximetry (SpO2) 72 Bit/second

Heart Rate 24 Bit/second

Blood Pressure 32 Bit/second

Ultrasound images 256 KBit/second

Video conference 25 KBit/second

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2.1.6 BAN Power Supply

The power supply block usually consists of a battery and a DC – DC converter.

Although batteries in the last decade have become smaller and less expensive, battery energy density does not scale exponentially as other technologies. Nevertheless, batteries are still a reasonable solution.

Alternative power sources must be explored. Fuel cells are a possible chemical alternative to lithium batteries. Advantage of such cell is they are able extend a node lifetime up to several times compared to usual batteries. However, many open research issues still remain to be addressed before microfuel cells can be used to power up sensor nodes. (Dyer, 2007) The disadvantages are such that they are noisy and must be improved in terms of robustness. Moreover, they pose safety issues (Benini, 2006) Also, they are still not yet available in a variety of configurations at low cost.

For indoor environments, rechargeable batteries may be the solution.

However, recharging the batteries may become burdensome especially for the elderly since they might tend to be forgetful at most of the time.

There are many options for harvesting energy from the environment instead of using energy stored locally on the node. The most common example is the use of solar cells for outdoor systems. Advantage of this source is that the solar cells can provide up to 15 mW/cm2 under direct sun (Amirtharajah et al, 2005), which is proven to be quite a large energy amount. However, the disadvantage of this source is such that the power density decreases in cloudy days and drastically reduces in indoor environment. Also, it cannot be used with body – worn sensors since sensors are preferred to be placed under the clothing at most cases.

Power also can be harvested from human – body motion, temperature, explicit interaction such as squeezing, shaking, pushing and pumping objects.

Electronic systems harvesting energy from ambient – radiation sources are another possibility. (Benini, 2006) However, disadvantage is such that they need to be close to the radiating source or benefit of a large collection area. Also, they collect only extremely limited power (less than 1 µW/cm2).

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Overall, there is no single energy source will fit all environments and applications. Thus, researchers must choose carefully one or a combination of power – sources depending on application requirements. Unused devices or components can be put into “sleep mode” and activated only when it is required. It is to optimize power consumption.

2.1.7 BAN Signal Measurements Principle

This research is mainly focusing on the signal measurements such as SpO2 (or pulse oximetry), temperature, heart rate (ECG) and blood pressure. In such a case, the researcher has to identify the use cases of BAN and clarify specific vital sign sensors to be mounted on patients.

(a) Blood oxygenation measurement (SpO2)

SpO2 or pulse oximetry is the measure of oxygen saturation in the blood, which is related to the heart pulse when the blood is pumped from the heart to other parts of the human body. When the heart pumps and relaxes, there will be a differential in absorption of light at a thin point of a human body. Oxygenated hemoglobin absorbs more infrared light waves and allows more red light waves to pass through. On the other hand, deoxygenated hemoglobin absorbs more red light waves and allows more infrared light waves to pass through. This unique property of hemoglobin with respect to red and infrared light wave allows oxygen saturation to be detected non – invasively. In such a case, sentinel events are defined when SpO2 is less than 85 %.

(Francis Tay, Guo, Xu, Nyan & Yap, 2009).

(b) Temperature measurement (oC)

Temperature taken at the ear closely matches the body core temperature compared to other pats of the body. This temperature is called is tympanal temperature. In such a case, the tympanal temperature gives us an indication of the state of the cognitive organ of a person – the human brain. Extended period of high fever can damage human organs, especially the brain. Thus, a precise thermopile was chosen in this application. Sentinel events are defined when temperature (oC) is greater than 38.3oC.

(Francis Tay, Guo, Xu, Nyan & Yap, 2009).

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(c) ECG monitoring

The standard ECG generally involves connection between 12 and 15 leads to a patient‟s chest, arms and right leg via adhesive electrodes. Disadvantage of such system is such that this device records only a short sampling of the heart‟s electrical activity which is not more than 30 seconds. Such short sampling time fails to capture cardiac activities that are irregular or intermittent, which is typical among ICUs and the elderly. (Mehmet, 2010)

Thus, a 3 – lead continuous telemetry based ECG is developed to evaluate a patient‟s cardiac activity for an extended period. Once a beat is detected, it is characterized by a number of features such as width, amplitude and R – to – R interval. Heart beat rate (HR) can be easily calculated by the R – to R interval.

(i) Heart beat rate :

Tachycardia : Heart rate > 90 beats/ min Bradycardia : Heart rate < 60 beats/ min (ii) QRS width :

0.1 – 0.12s indicates the Wolff – Parkinson – White syndrome or non – specific intraventricular conduction delay or incomplete right or left bundle branch block (RBBB or LBBB).

> 0.12 s indicates complete LBBB or RBBBB or ventricular tachycardia.

(iii) Q Wave

If Q wave‟s width is more than 0.04 s or/ and Q wave‟s height more than 25 % of R wave‟s height, it indicates myocardial infarction.

(d) Blood pressure measurement

Blood pressure measurement consists of the systolic and diastolic blood pressures.

Conventionally, blood pressure is obtained by using a cuff method utilizing Korotkoff principle. Other cuff methods make sure of pressure measurement in an oscillometry system. However, disadvantage is such that cuff is not suitable method for wearable application. This is because complex electronics and mechanical components have to be employed with pressure sensors that need to detect signals that fall in the range of milivolts. (Francis Tay, Guo, Xu, Nyan & Yap, 2009).

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Recently, a new cuffless method have been developed. The pulse transit time (PTT) is defined as time taken for pulsed blood, which is initiated from the heart, to travel to other parts of the human body where the plethysmogram (PPG) is taken.

The PTT is then used to infer the systolic blood pressure, which provides enough information for decision of hypertension and hypotension. Sentinel events is defined as below :

(i) Hypertension : > 140 / 90 mmHg (systolic / diastolic) (ii) Hypotension : < 90 / 50 mm Hg (systolic diastolic)

2.2 Prospective BAN contribution to patients and medical people

BAN has great potential in contributing to patients and medical people as well. First in place, it realizes connected health system. In such a way, patients can be connected to caregivers 24 hours via network according to needs of patients.

Secondly, BAN can be used to monitor chronic but stabilized patients ubiquitously meaning at home. Chronic patients discharged from hospitals are desperately in need of intensive monitoring at home. The cost of sending nurses or medical doctors to attend patients at home is very high. Therefore, remote monitoring of vital signs for home care becomes essentially useful especially for those patients. At the same time, it reduces chronicle disease patients‟ visit frequency to doctor‟s office.

Thirdly, there is a situation where hospital beds not being able to meet the number of patients to be admitted. BAN contributes in such a way that to monitor an after surgery patient vital signs (such as temperature and ECG) in a hospital wherever patient is located. In such a case, they are not critical as intensive care unit (ICU) patients but still require monitoring of vital signs. (Francis Tay, Guo, Xu,, Nyan & Yap, 2009).

Also, it can be in an automatic alert signal transmission from personal server to rescue centre by monitoring drastic vital changes in one‟s vital signs. The traditional cable sensors however, often cause inconvenience to patients by restricting patient‟s mobility and disturbing them with the presence of cables. To

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overcome this problem, wireless medical sensors are developed and applied. The special caregivers dependability will be decreased. (Alemdar & Ersoy, 2010) In such a case, this system will be not only monitoring system in everyday life, but also be a convenient system without limitation of movement.

It can identify emergency situations like heart attacks or sudden falls by real – time monitoring as well. It will detect if patient fell and alert the doctors or caregivers to avoid cases of lack of attention or late attention. It will suffice for saving lives considering that, without them these conditions will not be identified at all. With remote monitoring, this system can save the time and cost taken to the hospital. Today, time is same as money and competiveness. So, the patient may feel more comfortable. (Bong, Yong & Sun, 2008)

2.3 BAN International Applications

In a wider international context, BAN application can be extended to an even broader extent. Table 2.2 below shows some of the in – body and on – body applications.

Table 3: In – Body and On – Body Sensor Networks Applications (Ullah, Khan , Saleem, Higgins & Kwak, 2009)

Application Type

Sensor Node

Data Rate

Duty Cycle (per device) %

per time

Power Consumption

Privacy

In – body Applications

Glucose Sensor Few Kbps < 1 % Extremely

Low

High

Pacemaker Few Kbps < 1 % Low High

Endoscope Capsule >2 Mbps < 50 % Low Medium

On – body Medical Applications

ECG 3 kbps < 10 % Low High

SpO2 32 bps < 1 % Low High

Blood Pressure <10 bps < 1 % High High

On – body Non – Medical Applications

Music for Headsets 1.4 Mbps High Relatively

High

Low

Forgotten Things Monitor

256 kbps Medium Low Low

Social Networking <200 kbps < 1 % Low High

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The following part discusses some of the BAN international applications:

2.3.1 Cardiovascular diseases detection applications

Traditionally, Holter monitors were used to collect cardio rhythm disturbances without real – time feedback. However, transient abnormalities are sometimes difficult to capture. For instance, many cardiac diseases are associated with episodic rather than continuous abnormalities and their time cannot be accurately predicted.

Such episodic abnormalities can be transient surges in blood pressure, paroxysmal arrhythmias or induced episodes of myocardial ischemia. The advantage of BAN system in such a case is such that patients can be monitored under natural physiological states, over a long term period for their heart activity. Also, the patient can be monitored for an ambulatory period without being constrained physically.

2.3.2 Cancer detection applications

Cancer remains one of the biggest threats to the human life. In such a case, sophisticated technology allows a set of miniaturized sensors capable of monitoring cancer cells to be seamlessly integrated in a BAN. This allows physician to diagnose without biopsy. (Ullah, Khan, Saleem, Higgins & Kwak, 2009)

2.3.3 Diabetes detection applications

A BAN network on a diabetic patient could auto inject insulin through a pump, as soon as his insulin level declines, thus making the patient „doctor – free‟ and virtually healthy.

2.3.4 Asthma detection applications

A BAN can help asthma patients by monitoring allergic agents in the air and providing real – time feedback to the physician. Chu et al proposed a GPS – based device that monitors environmental factors and triggers an alarm in case of detecting information allergic to the patient (Ullah, Khan, Saleem, Higgins & Kwak, 2009) 2.3.5 Artificial retina applications

Retina prosthesis chips can be implanted in the human eye that assist patient with limited or no vision to see an adequate level. (Ullah, Khan, Saleem, Higgins & Kwak, 2009)

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2.3.6 Sleep disorder detection applications

If monitoring is carried out during ordinary daily life, data have to be collected routinely and automatically without constraining the subject. It is expected that people will be in a stable physiological condition during sleep, and that the sleep period is long enough for physiological observations. (Ogawa & Togawa, 2000) Example of existing project:

SleepScan is recently developed by Japanese Tanita company. It is a wireless sensor-equipped mat to measure the deepness and quality of sleep. In such a case, it is designed to monitor heart rate, respiration rate and motion in bed and to record these data during night time so that to help detecting sleeping disorders such as insomnia. The concept is as easy as slipping it under patient‟s mattress and based on information coming from the capacitor microphone inside the mat that tracks vibrations. The collected data is stored on a removable SD card allowing it to be uploaded and analyzed on a PC via an included piece of software. The advantage of such system is such that this system is a convenient system without limitation of movement. This, improves the quality of healthcare as well. In comparison, the traditional EEG method is an invasive method to diagnose any sleep disorders among patients. Rather than precise measurement, this SleepScan system can provide long term monitoring without disturb the sleep quality of patients.

2.3.7 Medication intake monitoring applications

Medication noncompliance is common in elderly and chronically ill especially when cognitive disabilities are encountered. Therefore, medication intake monitoring is essential. One of the early prototypes developed by Moh et al. (2005) aim to control the medicine intake of the elderly with the combined use of sensor networks and RFID. In such a case, the system is able to determine when and which bottle is removed or replaced by the patient and the amount of medicine taken. In such a case, the patient wearing an Ultra High Frequency (UHF) RFID tag is identified and located by the Patient Monitoring Subsystem and the system is able to alert the patient to take the necessary medicines.

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2.3.8 Medical status monitoring applications

Monitoring the medical status of the people is the most widely studied application type of pervasive healthcare systems. The commonly used vital signs are ECG, pulse oximetry, body temperature, heart rate and blood pressure. The acceleration data is also used together with these vital signs in some studies. In maintaining the health of elderly people, it can be useful to monitor their health status through their daily routine in their own home, as well too. (Ogawa, Suzuki, Otake, Izutsu, Iwaya &

Togawa, 2002)

Examples of existing projects:

(a) MobiHealth is one of the early projects that integrates all the wearable sensor devices such as PDA‟s mobile phone and watches that a person carries around during the day. MobiHealth is important in being one of the early studied proposing the convergence of different network systems like BAN, PAN and WAN to enable personalized and mobile healthcare.

(b) CodeBlue is a hardware and software platform developed at Harvard University. The design includes a mote – based pulse oximeter, 2 – lead ECG and a motion analysis sensor board. CodeBlue project is one of the most comprehensive projects in the literature which includes mote design, software architecture design, ad hoc network design and multi – hop communication together with location tracking.

(c) LifeGuard, which was developed for astronauts in the first place, can also used for general vital signs monitoring. The system is comprised of 3 components. The sensors part can support different types of sensors such as ECG, respiration, pulse oximeter and blood pressure.

(d) FireLine is a simpler prototype design. It is designed for monitoring cardiac measurements of firefighters for being able to take the necessary actions in the case of abnormality. The device is composed of a wireless sensor, a heart rate sensor and 3 electrodes.

(e) MEMSWear – biomonitoring system is developed by National University of Singapore. Microelectro – mechanical systems (MEMS) integrate mechanical elements, sensors, actuators and electronics through microfabrication technology. In such a case, MEMSWear is a wearable shirt,

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which is equipped with physiological sensors for human physiological signs, which is ECG, SpO2, body temperature and blood pressure. The advantage of such intelligent biomedical cloth is such that biosensors are embedded inside cloths for measuring physiological signals and to provide immediate diagnosis and trend analysis. Although embedding the sensors into the garment could provide a convenient wearable system for the patient, the disadvantage is such that it is not flexible for the addition or relocation of sensors. Different sizes of clothes have to be designed for different person, which can cause cost burden. (Benny Lo & Yang, 2008)

2.3.9 Predictive diagnostic applications

In the case of predictive diagnostic in maintenance health systems, there are many types of diseases but only percentage of them we can predict by technique.

With the help of embedded system capabilities, we can predict some life endangering situation like allergic reaction, coronary thrombosis, hypoglycaemic shock and sudden death syndrome. For example, the sudden death syndrome can be predicted from ECG signal, temperature, breath frequency and blood oxygen saturation. Also, prediction of blood pressure and blood glucose can prevent from hypertension shock and hyper or hypoglycaemic shock. (Srovnal & Penhaker, 2005) 2.3.10 Biomedical feedback control systems applications

It is well known that there are other indirect physiological parameters that can be measured. In such a case, BAN is to provide an indirect indication of the key parameters that require close monitoring or regulation. Examples of such indirect parameters include end tidal carbon dioxide tension, oxygen saturation in blood and glucose concentration in interstitial fluid. Methods of soft computing can be applied to combine continuous measurement of indirect parameters to produce sensors that can provide continuous estimation of the key physiological parameters. (Srovnal &

Penhaker, 2005)

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2.4.10 Location tracking applications

Location tracking for pervasive healthcare systems may serve both indoor and outdoor applications. In an indoor scenario, the location tracking system can be integrated for increasing the context – awareness of the systems and for efficiency. In an outdoor setting, it can be used for assisting people with cognitive disabilities or identifying the locations of people when an alarm situation has occurred like an epilepsy seizure. In such a case, the system works by placing passive RFID tags in important locations where patients need to make decisions about the next action to take, such as turn right or left. The visited positions are tracked and logged and in case of anomalies, alarms are raised. (Alemdar & Ersoy, 2010)

Examples of existing projects:

(a) Ultra Badge System is location tracking application that is used in a hospital setting. In Ultra Badge, a 3D tag system designed to realize the location of the patients. When a patient is in a specific area where a fall is most likely to occur (such as at the entrance of a toilet), the system alerts the caregivers.

(b) ALMAS project integrates location tracking technology with video analysis and wireless multimedia technologies to create an environment that provides healthcare for the elderly. It consists of a wireless wearable unit, RFID tag, wireless transceivers and video cameras. ALMAS‟ video cameras continuously record the activities of the patient and automatically detect if there is a situation that requires attention by the healthcare professional.

2.4.11 Battlefield applications

Other than in medical field, BAN can also be used to connect soldiers in a battlefield and report their activities to the commander. For example, the activities can be running, firing and digging. The soldiers should have a secure communication channel in order to prevent ambushes. (Ullah, Khan, Saleem, Higgins & Kwak, 2009)

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2.4 Challenges

2.4.1 Hardware Level Challenges 2.4.1.1 Unobtrusiveness

When the patients have to carry sensors attached on their bodies, unobtrusiveness poses a major challenge. In such a case, the need for integrating different sensors into one solution makes it even difficult. For example, the body – worn sensor devices are heavy yet obtrusive devices, whereas the bandage type ECG sensors are much easier wearable devices (Alemdar & Ersoy, 2010). Hence, the design and development of wearable yet unobtrusively sensor devices is crucial. It is expected that the sensor nodes could become miniature in order to avoid activity restriction with new integration and packaging technologies. (Huang et al, 2009)

2.4.1.2 Sensitivity

Sensitivity of the sensor devices is important especially when the users wear the sensors under harsh environments like in a fire situation or exercising. In such a case, the transducer of the sensor devices can be affected negatively by the sweat, causing the sensitivity reduction of the sensors or requiring further sensor recalibration. It is expected that low – maintenance and highly sensitive vital signs monitoring sensors are developed in the near future. (Alemdar & Ersoy, 2010)

2.4.1.3 Energy

The lifetime of batteries becomes one of the bottlenecks of sensor devices. In such a case, the wireless communication link is the most power demanding part of the BAN.

Reducing the power consumption of the RF transducer could significantly reduce the power consumption and extend the lifetime of the sensor node. (Benny Lo & Yang, 2008)

For indoor environments, rechargeable batteries may be the solution.

However, recharging the batteries may become burdensome especially for the elderly since they might tend to be forgetful at most of the time. Apart from designing low – power sensors, we still need energy scavenging techniques (Yoo, Yan, Lee, Kim, &

Yoo, 2010). In such a case, the solar cells can provide up to 15 mW/cm2 under direct

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sun, which is proven to be quite a large energy amount. But after all, it cannot be used with body – worn sensors since sensors are preferred to be placed under the clothing at most cases. Therefore, motion and body heat based energy scavenging techniques should be developed to prolong the sensor operating life.

2.3.1.4 Data acquisition efficiency

We have to pay special attention on the efficiency of data processing techniques. In some cases, a 3 – axes accelerometer may not be capable of classifying all activities of the people whilst 3 – lead ECG may be insufficient for identifying a cardiac disease. Thus, more sensors will be needed in order to increase the data accuracy.

The real – time acquisition and analysis of the physiological data is essential.

(Alemdar & Ersoy, 2010) 2.3.1.5 Reliability

The reliability of the system is important factor. In such a case, an undetected life critical signal could be fatal. The improvement of reliability can minimize sensing and read – out errors, avoiding errors in wireless communication as well. (Huang et al, 2009)

2.4.2 Layer Independent Challenges

There are some challenges that are not directly related with a specific layer yet they have to be solved for the improvement of BAN system. The challenges and their solutions are discussed in the following subsections.

2.4.2.1 Security / Privacy

The confidentiality, data integrity, accountability and access control are the fundamental security requirements of the BAN system. In order to protect patient‟s privacy, the security of BAN should be guaranteed into such an extent that the sensed signal from the body should have secure yet limited access. Also, the sensed signal from one person should not be mixed up with another person. (Huang et al, 2009) The privacy preserving methods should be developed for the comfort of the monitored people. (Alemdar & Ersoy, 2010)

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2.4.2.2 User – friendliness

The development of natural interfaces between a diverse group of people and pervasive systems are crucial. In such a case, the system should be easy for patients to use with minimal training and minimal maintenance. The power consumption should be minimized to eliminate the recharging inconvenience. It should be portable so that patients can take the system anywhere, anytime. (Blount et al, 2007)

2.4.2.3 Cost

Cost is the most frequently discussed issue. Unless the system is affordable or it has cost offset, it may not be widely accepted and adopted even if it is deemed useful.

(Steele, R., Lo, A., Secombe, C., Wong, Y.K., 2009)

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CHAPTER 3

METHODOLOGY

3.1 Introduction

The aim of this chapter is to define the methods of research. In such a case, the process involves the source of data, research strategy, questionnaire design and the technique to analyze the collected data. The methods used to conduct this research are primary and secondary research. The primary research method used is questionnaire survey whilst the secondary research method used to support and to compare the primary results was intensive interview. A flow chart of this research is included at the end of this chapter in order to depict how the process of this study to be undertaken from the inception to the completion.

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3.2 Source of data

Source of data is defined in which the required information can be obtained in order to compile this study in a more thorough way. It can be classified into 2 categories as following:

3.2.1 Primary Data

Primary data is the data to address the specific problem at hand – the research question. In this BAN study, the raw data are collected through survey questionnaire.

The major advantage of primary data is accuracy of data since it is collected by the researcher. The disadvantages of primary data are costly and time consuming (Donald and Pamela, 2006)

3.2.2 Secondary Data

Secondary data are data originally collected to address a problem other than the one requires the researcher‟s attention at the moment. The data are ready made data which collected from references books, newspapers, journals, magazines and internet in order to realize the existing information and issue on current BAN technology.

The advantage of secondary data is quicker and cheaper than primary data. The disadvantage is the information may not meet specific needs for this BAN study (Donald and Pamela, 2006)

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3.3 Selection of Research Strategy 3.3.1 Literature Review

The literature review form part of this research. One way of attaining this kind of information is through the current mass media and publications. Reviews and analysis were conducted on articles, journals, reports and the internet. These reviews are important in such a way that they provide the latest development especially from the biomedical field. This method will increase the knowledge about this study and provide a better yet in – depth understanding. These reviews and analysis also helped in formulating the questionnaire survey, too.

3.3.2 Questionnaire Survey

In this research, method of acquisitive information used was questionnaire. In such a case, a set of questionnaire has been designed based on criteria of particular research paper in fulfilling objectives of this paper. In this survey, postal questionnaire is not chosen because it may take several weeks to collect the responses and normally response rate is usually less than 5 %. Also, phone interviews are not chosen as the respondents are obligated to the time slots provided by the researcher. Thus, the questionnaire was best conducted in a face – to – face interview form.

There are a variety of designs for scaled response and hence the design options need to be considered by the researcher. One of the most common scaled – response formats is the Likert scale. It is developed by Rensis Likert in an attempt to improve the levels of measurement in social research through the use of standardized response categories in survey questionnaires. A common form is an assertion, with which the person may agree or disagree to varying degrees. It is typically a five point scale, as shown in the following format:

a) Very important b) Important c) Average d) Not important e) Very not important

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The major advantage is such that questions used are easy to understand and so lead to consistent answers. By using such likert scale, the researcher can avoid choices of “Don‟t Know”, Neutral or Undecided response category. However, a disadvantage is that only a few options are offered, with which respondents may not fully agree. Also, a problem may arise where people may become influenced by the way they have answered previous questions. For example, they may continue to agree if they have agreed several times in a row. (Changing Mind Organization, 2010)

In this research, there are 3 main target end users, which are in – patients including medical tourism, out – patients and health conscious people as well. Thus, this questionnaire is mainly consisted of 5 parts to know the design requirements of BAN.

(i) Section 1 is related to the application of BAN to in-patients (including medical tourism)

(ii) Section 2 is related to the application of BAN to out- patients

(iii) Section 3 is related to the application of BAN to health conscious people.

(iv) Section 4 is related to the physical requirements for the BAN design.

After finalizing the entire research questionnaire, the photocopies of questionnaires are completed along with face-to-face interview. The answers are filled up by the researcher based on the participating respondent‟s response. The participating respondent in this research were 30 (medical doctor: 10, biomedical engineering personnel: 20). In such a case, the researcher has to identify the use cases of BAN and clarify specific vital sign sensors to be mounted on patients. The functional specifications and design requirements may differ to suit different medical procedures. All these matters have to be discussed with medical doctors and biomedical engineering personnel from Malaysia‟s private and government hospitals (in this BAN research, Kuala Lumpur and Penang are chosen as the main surveyed destinations). Based on the ascertained design requirements, the researcher shall then have a clear concept in developing a BAN based, human friendly, connected health system.

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3.4 Data analysis 3.4.1 Importance Index

Qualitative data such as likert scale can be measured using a 3 points, 5 points measurement scales. In this research, the 5 points likert scale is being used.

Qualitative data can be converted to quantitative data using the following adopted from Lim & Alum (1995) (NTU, Singapore) published in the International Journal of Project Management (Lim, E.C. Alum, J., 1995).

Conversion Formula = 5N1 + 4N2 + 3N3 + 2N4 + N5 5 (N1 + N2 + N3 + N4 + N5) N1 = Number of respondents with strongly agree N2 = Number of respondents with agree

N3 = Number of respondents with average N4 = Number of respondents with disagree

N5 = Number of respondents with strongly disagree

3.5 Conclusion

Data will be gathered through primary and secondary data collection method with the purpose to find out the respondent‟s response on BAN design requirement.

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3.6 Flow Chart of Research Progress

Selection of Research Title:

Design Requirement Clarification of Body Area Network (BAN)

Source of Data

Primary Data : Secondary Data :  Survey Questionnaire  Reference Books (which is carried in an face-to  Newspapers face interview form)  Journal articles  Magazines  Internet

Preparation of Project II : Preparation of Project I :  Findings and analysis  Introduction

 Literature review  Literature Review  Conclusion and  Research Methodology Recommendation

Compilation of research

The end

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CHAPTER 4

DATA ANALYSIS

A total of 30 sets of questionnaire were carried out. It is mainly comprised of the hospital, biomedical companies and clinics which located within Kuala Lumpur and Penang area. The questionnaire was aimed to obtain ascertained design requirement which is important for us to develop a Body Area Network (BAN) – based system.

Eventually, 25 questionnaires responded were returned, it represents rate of 83.33%.

Hence, this analysis is carried out based on the 25 completed and returned questionnaires. Following is the list of hospitals or companies or clinics which are included in questionnaire surveys :

Table 4: List of Hospitals and Companies Included in Questionnaire Surveys

No. Hospitals / Clinics Location

1 Gleeneagles Intan Medical Centre (GIMC) Kuala Lumpur

2 Hospital Kuala Lumpur (HKL) Kuala Lumpur

3 Hospital Tawakal Kuala Lumpur

4 Hospital Pusrawi Kuala Lumpur

5 Hospital Universiti Kebangsaan Malaysia (HUKM) Kuala Lumpur

6 Tung Shin Hospital Kuala Lumpur

7 Ampang Puteri Specialist Hospital (APSH) Kuala Lumpur

8 Faculty of Medicine, Universiti Tunku Abdul Rahman (UTAR) Kuala Lumpur

9 Hospital Pulau Pinang Penang

10 Penang Adventist Hospital (PAH) Penang

11 Gleeneagles Medical Centre (GMC) Penang

12 Loh Guan Lye Specialist Centre (LSC) Penang

13 Hospital Mutiara Pantai Timur Penang

14 Klinik Lim Sungai Pinang Penang

No. Biomedical Services / Equipment Companies Location

15 Healtronics (M) Sdn Bhd Kuala Lumpur

16 Schiller (M) Sdn Bhd Kuala Lumpur

17 Radicare (M) Sdn Bhd Kuala Lumpur

18 UMC SrviceMaster (M) Sdn Bhd Penang

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4.1 Respondent’s Demographics

This section evaluates working experience, occupation or position and the nature of service of the questionnaire‟s respondents.

4.1.1 Years of Working Experience Among Respondents

Figure 1: Years of Working Experience among Respondents

This data analysis examines working experiences among respondents. This is to ensure the reliability of data obtained from the questionnaires. Since this is a qualitative based surveys, respondent‟s working experience are important in contributing to the accountability and reliability of data obtained.

The data analysis was indicating the greatest number of the respondent‟s working experience is at the range of 5 – 10 years which consists of 60% (15 respondents). On the other hand, the least number of the respondent‟s working experience is less than 3 years, which comprises only at 4% (1 respondent). Range of 10 – 20 years consists of 20% (5 respondents) which is the second highest among all the categories. Besides, other range of working experience such as the range of 3 – 5 years and those more than 20 years both comprise 8% of the questionnaires (2 respondents).

Rujukan

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